Tim Knaup 1947 Plymouth Special Deluxe

[Tim Knaup]

I have been working on a 1947 Plymouth Special Deluxe from my father in law that had been stored for the past 10+ years. It has a 1941 engine in it from the factory (WWII leftovers) and he had the engine rebuilt prior to storage. When he had run the vehicle all ran well with no issues. Later on, the electric fuel pump he had in it to bypass the mechanical one eventually failed and he did not have it replaced. Brakes froze up and it needed some work. I have done a complete brake replacement. also replaced coil, distributor cap, rotor plugs & wires, points and condenser, starter rebuild, electric fuel pump (pressure regulator on fuel line, new fuel filters.  Vehicle starts and runs well at lower RPM but when I get about to 30 mph or so, it loses power and misses. Thought it might be timing but when adjusted still does the same. Fuel pump seems to be delivering fuel well but cant determine that when the vehicle is under load. Any thoughts on this?

[desoto1939]

what abut vacuum advance. Is it set at the correct timing mark. What are the points set at and the gapping onthe plugs. Is there an sisson choke onthe manifold and is this adjusted properly anything sticking inthe carb. Did you rebuild it correctly, there are two small ball bearings and if you switch them into the wrong location can cause issues.  Did you soak the accelerate pump leather in light oil?  Any air leaks around the manifold and base of the carb. Did you put the correct base gasket back onthe bottom of the carb at the manifld Should have the slotted gaset since you are not running any govenor onthe car.

 

Just some thoughts.

 

rich Hartung

desoto1939@aol.com

[Tim Knaup]

I had a couple mechanics work on it with me. We disconnected the vacuum advance and plugged it to set the timing. According to the mechanic, he checked the vacuum line and it was creating vacuum when we ran up the rpm. I had one of our shop mechanics rebuild the carb (he works on old cars on the side). put the same gasket back on the base of carb since it looked good. No leaks we can see around the manifold or carb base, although the carb is not far from needing replacement in my mind. the choke was replaced with a manual cable operated choke before I received the vehicle. Could an incorrectly set dwell cause this problem? When i bought the fuel pump, an plymouth guru at NAPA told me I should also buy a fuel pressure regulator valve and install in line, which I did, and set it down low. That does not seem to be the problem. My next step was to adjust dwell and get a pressure gage for fuel and check to see how well the fuel pump was delivering fuel. 

[Merle Coggins]

Double check your points spring. I had it happen to me. I didn’t get the spring hooked properly and there was very little spring tension. It would start and run great at lower RPM. when it got up around 2000 RPM the points would start to float and the timing would go crazy. Engine would loose power, cough, and sputter. 

Edited September 25, 2020 by Merle Coggins

[plymouthcranbrook]

If it sat for a long time it is possible there is a partial blockage In a fuel line or filter that lets enough fuel through For light operation but not enough for higher loads.  Did you clean the tank?  Maybe blow out the lines and check or replace the filter?  It most likely has an  external one iF an electric pump is installed.  There is a filter of sorts in the tank as well so a little air back through the line might help. Is the issue higher rpms in any gear or just third.
Might also just be crappy Chinese parts. Where did you get the tune up stuff? 

[knuckleharley]

3 hours ago, Tim Knaup said:

  Any thoughts on this?

Is the gas tank the original one? If so,did you remove it,have it boiled out and re-coated inside and out before installing it and putting new gas in it?

 

Are all your gas lines,both rubber and steel new,or are you still using the old ones?

[Wes Flippen]

Had the exact same issue with my '50 Coronet, ran great up to about 30-35, then started missing terribly. Removed points and installed a pertronix, no more problems. I believe the springs in the points plate were worn and to be honest didn't want to be messing with points.

Wes